The present invention relates to a magnetic disk cartridge for rotatably containing a disk-form magnetic disk within a hard case, and a producing method therefor.
A magnetic disk cartridge of this kind has been increasingly used for memory means for a computer.
A floppy disk has been used for memory means for a computer and it comprises a flexible jacket made of a synthetic resin material such as a vinyl chloride and a disk-form magnetic disk which is rotatably held therein, in which the jacket is provided with windows for a magnetic head and a driving means for rotating the magnetic disk. Therefore, when the jacket is bent during its handling, the magnetic disk contained therein is damaged. Further, there is a danger of contacting the magnetic disk contained in the jacket with a finger or the like inserted therein through the windows, with the result of damaging the record stored in the magnetic disk. Hence, it must be handled with the greatest possible care.
Then, in order to remove the defects of the floppy disk, a hard-type magnetic disk cartridge has been developed, which comprises a hard case made of a synthetic resin material and a disk-form magnetic disk which is rotatably contained therein, in which the magnetic recording medium of the magnetic disk may not be exposed to outside through an opening of the case.
In FIGS. 1 and 2, there is shown a conventional hard-type magnetic disk cartridge comprising a hard case which is composed of a cover member 1 and a bottom member 2, and a disk-form magnetic disk 3 which is rotatably contained in the hard case. The cover member 1 and the bottom member 2 are made of a hard synthetic resin material by molding, which posesses a larger mechanical strength than that of the flexible magnetic disk jacket mentioned above, and thus it is hard to allow the case to deform by bending. Accordingly, the cartridge can protect the magnetic disk 3 contained within the hard case thereof more exactly and reliably as compared with the flexible magnetic disk jacket.
On the inner surfaces of the cover member 1 and the bottom member 2, liners 4 and 5 which are generally made of a soft material, are attached on the opposite sides of the both surfaces of the magnetic disk 3. The case composed of the cover member 1 and the botttom member 2 contains a space 6 having a height H.sub.1 which is larger than a thickness t.sub.1 of the magnetic disk 3.
The bottom member 2 is provided with a circular opening 21 in its center positioned along a pivot center O, and an anti-abrasion chip 7 having a circular form is attached to the inner center of the cover member 1. The circular anti-abrasion chip 7 prevents the direct contact of the pivot shaft of the disk drive means with the inner surface of the cover member 1 when writing and reading the record in and from the magnetic disk 3, in order to prevent the abrasion of the inner surface of the cover member 1. The cover member 1 is coaxially provided with a circular ring projection 101 projecting inside at a certain distance around the circular anti-abrasion chip 7 attached to the inside of the cover member 1.
As shown in FIGS. 3 and 4, the cover member 1 and the bottom member 2 are further provided with windows 8 and 9, respectively, one for each member, in their corresponding position, through which the magnetic head may be inserted. The windows 8 and 9 are closed by shutters 10 when they are not used, as shown in FIG. 1.
The magnetic disk 3 comprises a stepped hub portion 31 in its center, which is made of a metal or a synthetic resin material, and a doughnut circular ring-form magnetic recording medium 32 which is coaxially connected to the periphery of the hub portion 31. The hub portion 31 is provided with an opening 33 in its center, through which the pivot shaft of the magnetic disk drive means is inserted. When the magnetic disk 3 is contained in the case, the circular ring projection 101 of the cover member 1 is positioned inside of the inner diameter part of the hub portion 31 of the magnetic disk 3 and the outer surface of the hub portion 31 is exposed to the central circular opening 21 of the bottom member 2 so that the magnetic recording medium 32 of the magnetic disk 3 may be completely covered by the cover member 1 and the bottom member 2 therebetween.
As shown in FIG. 5, when the above described magnetic disk cartridge is worked, a pivot shaft 11 of a magnetic disk drive means (not shown) is inserted into the central opening 33 of the hub portion 31 of the disk 3 so as to abut against the anti-abrasion chip 7 attached to the center of the cover member 1, and the disk drive means is driven to rotate the pivot shaft 11, thereby rotating the magnetic disk 3 within the case. On this occasion, the windows 8 and 9 are opened by drawing the shutters 10, and the magnetic heads are inserted into the case through the windows 8 and 9 to write and read the record in and out of the magnetic disk 3.
In the conventional hard-type magnetic disk cartridge described above, since the cover member 1 and the bottom member 2 are made of the hard material, the protecting function for the magnetic disk 3 is very high, and, since the shutters 10 and the hub portion 31 are positioned at the head inserting windows 8 and 9 and the pivot shaft inserting opening 21, the magnetic recording medium 32 of the magnetic disk 3 is completely covered by the cover member 1 and the bottom member 2 without exposing it to the outside. Accordingly, the protecting function for the magnetic recording medium of the magnetic disk is far higher as compared with the conventional floppy disk. Further, since the tip of the pivot shaft 11 of the disk drive means is received by the anti-abrasion chip 7 in contact therewith, when the pivot shaft 11 is rotated, the abrasion of the cover member 1 by the pivot shaft 11 can be effectively prevented during the writing and the reading of the record of the magnetic disk 3.
However, in this case, since the shape of the anti-abrasion chip 7 is circular, the anti-abrasion chips 7 are obtained by punching or cutting a circular shape from a belt-form anti-abrasion sheet 12 which is attached to a base sheet 13 such as a paper sheet and which is usually treated by an agent such as silicone so as to readily peel off, as shown in FIG. 6. Thus, in this case, the disuse portion 14 of the anti-abrasion sheet 12 is rather much, which is not economical because the anti-abrasion material is generally high in cost, and which is therefore very disadvantageous for performing the cost-down of the finished magnetic disk cartridge and becomes a large obstacle therefor.